Recently, a mammography system which takes a radiographic image of a breast using X-ray, such as the X-ray, has been used for the examination of breast cancer. However, since the image obtained in the mammography system is a plane image, discrimination is sometimes difficult in a case in which a tumor or a calcified portion overlaps, for example, a mammary gland tissue.
For this reason, a computed tomographic mammography system capable of obtaining a three-dimensional (3D) tomographic image by reconstructing a plurality of pieces of image data using computed tomography (CT) has been developed.
A computed tomographic mammography system disclosed in PTL 1 has been proposed. This computed tomographic mammography system includes: a bed for image taking provided with an opening through which a testee puts the breast in a breast chamber; an X-ray tube and an X-ray detecting device which are rotated about the breast chamber, and a rotation driving unit which drives the X-ray tube and the X-ray detecting device to rotate. The X-ray tube and the X-ray detecting device take an X-ray radiographic image at predetermined angles while cooperatively rotating about a rotation axis which passes inside the breast chamber in a direction in which the testee puts the breast in the breast chamber through the opening. Lines 19 and 20 of the 11th column of the specification of PTL 1 describe a computed tomographic mammography system which uses an X-ray source in which a reflective X-ray tube “varian Rad 71” having a rotating anode type anode is housed in a container “Mamrad 100.” This X-ray source is disposed to be rotatable about a rotation axis which overlaps a breast chamber.
Further, lines 17 to 19 of the 11th column of the specification of PTL 1 describe providing a distance of 7 cm as a distance between an end of the X-ray source on the testee side and a focal point, and providing a 25-mm-deep bowl-shaped recess in the bed for image taking in order to bring the chest close to an exposure area.